Onigiri or Omusubi is THE soul food of Japan for a long long time. For my age group (above 60s), it was basically a home cooking item instead of professionally served food item like you guys are experiencing via convenient stores or restaurants. It's a soul food 'cause an expression of love of mother toward her family members is involved in the making of each onigiri. Then it was duly appreciated outside of home, by the eaters at the occasions of picnic and outdoor event etc. So it's like a home made sandwich for westerners. BTW, when I was kid, onigiri were lapped in the bamboo leaves, so there were no environmentally problematic garbages left afterwards as well.